Positioning apparatus and method of use

ABSTRACT

A positioning system having a base, a manually movable end effector and a first joint interposed between the base and the end effector is disclosed. The first joint may comprise a proximal portion and a distal portion coupled together by magnetic attraction and configured to be intermittently separated by a pressurized gas cushion. The first joint may be configured to be changeable between a movable state and a fixed state. In the movable state, the proximal and distal portions are separated by the pressurized gas cushion and are movable relative to each other. In the fixed state, the proximal and distal portions contact each other and relative movement is thereby impeded. 
     Methods of precisely positioning an end effector may include providing a device having a base, a first joint located distally from the base, and an end effector located distally from the first joint. The first joint may have two portions separated by a gas cushion, the first joint allowing the end effector to be movable with respect to the base. The method may further comprise manually positioning the end effector, and removing the gas cushion to cause the two joint portions to contact each other, thereby locking the end effector in the precise location in which it was positioned.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/503,727, filed Jul. 15, 2009, which is herein incorporated byreference in its entirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

FIELD

This invention generally relates to precise positioning devices, inparticular articulating devices that can be moved into a particularconfiguration and accurately locked in that orientation.

BACKGROUND

The need to precisely position a device occurs in many fields ofendeavor. One such field is surgery, in which an instrument may need tobe precisely positioned relative to a patient undergoing an operation ordiagnostic procedure. For example, there is a need to enable an earsurgeon, such as an otologist, to precisely position and manipulateinstruments in an around the structures of the ear, particularly theinner and middle ear.

Other more general medical applications of precise positioning devicesinclude those that enable medical personnel to adjustably positionimaging, therapeutic, and other instruments at desired locations in andnear a patient's body. Such positioning needs arise in ophthalmic,neurological, orthopedic and other medical fields. Even more generally,requirements for precise positioning of an object frequently occur inthe field of optics, measurement and manufacturing.

What is desirable, and not provided by prior art methods and devices, isa means for precisely positioning an object in a particular orientationwith a support mechanism, and accurately fixing the object in thatorientation.

SUMMARY OF THE DISCLOSURE

According to aspects of the present description, a support device maycomprise one or more moveable links interconnected by selectivelylockable joints. The selectively lockable joints allow the linkagemechanism to be manually or otherwise moved to a desired configurationor position while the joints are unlocked, and then to become a partlyor fully fixed configuration when some or all of the joints are locked.

In some embodiments, a positioning system comprises a base, a manuallymovable end effector and a first joint interposed between the base andthe end effector. The first joint may comprise a proximal portion and adistal portion coupled together generally by magnetic attraction andconfigured to be intermittently separated by a pressurized gas or otherfluid cushion. The first joint may be configured to be changeablebetween a movable state and a fixed state. In the movable state, theproximal and distal portions are separated by the pressurized gascushion and are movable relative to each other in at least one degree offreedom. In the fixed state, the proximal and distal portions contacteach other and relative movement is thereby impeded.

In some of the above embodiments, the proximal and distal portions ofthe first joint may rotate relative to each other in at least tworotational degrees of freedom. The first joint may be a spherical joint.The spherical joint may be capable of movement in three degrees ofrotational freedom. In some of the embodiments, the system is configuredwithout a prime mover to position the end effector.

In some of the above embodiments, the system may further comprise asecond joint interposed between the base and the end effector in serieswith the first joint. The second joint may have at least one degree ofrotational freedom. Each of the first and second joints may comprise aseparately interruptible pressurized gas cushion. In some embodiments,the second joint comprises a proximal portion and a distal portion, andthe distal portion of the first joint is coupled to the proximal portionof the second joint by a rigid link. The rigid link may include aninternal channel in fluid communication with both the distal portion ofthe first joint and the proximal portion of the second joint. The rigidlink may comprise two or more ends and at least one orifice at each ofthe ends, wherein each of the orifices is in fluid communication withthe internal channel and a gas cushion of one of the joints, and theinternal channel may have a cross-sectional area that is larger than thecross-sectional area of each of the orifices in order to create a plenumchamber to store or damp gas flow. In some of these embodiments, theinternal channel cross-sectional area is at least four times as large asthe lateral cross-sectional area of each of the orifices.

In some embodiments, the system may comprise at least a second jointinterposed between the base and the end effector in parallel with thefirst joint. The first and/or second joints may be spherical, planar,cylindrical or other types of kinematic, joints. In some embodiments, asphere, planar, cylindrical or other kinematic member serves as a commonproximal portion for the first and second joints.

In some embodiments, a positioning system includes at least two parallellinks interposed between the base and the end effector. Each of theparallel links may include at least two joints, and each of the jointsmay be changeable between a movable state and a fixed state.

In some of the above embodiments, the end effector is configured with alumen for slidably receiving an instrument. In some embodiments, aminiature endoscope instrument may be provided that has a first portionconfigured to be precisely received within the end effector lumen and asecond portion configured for entering a human cochlea. In some of thesystems, the base is configured for attaching to a temporal bone.

In some of the above embodiments, the pressurized gas cushion has athickness of no more than about 50 microns. In other embodiments, thepressurized gas cushion has a thickness of no more than about 5 microns.In still other embodiments, the pressurized gas cushion has a thicknessof no more than about 1 micron.

According to aspects of the detailed description, methods of preciselypositioning an end effector may include providing a device having abase, a first joint located distally from the base, and an end effectorlocated distally from the first joint. The first joint may have twoportions separated by a gas cushion, the first joint allowing the endeffector to be movable with respect to the base. The method may furthercomprise manually positioning the end effector, and removing the gascushion to cause the two joint portions to contact each other, therebylocking the end effector in the precise location in which it waspositioned.

In some of the above methods, the manual positioning step comprisesmoving the end effector in at least two degrees of rotational freedom.The two portions of the joint may be mutually attracted by a magneticforce. The first joint may be a spherical joint. In some of the methods,the device comprises a second joint located distally from the firstjoint and proximally from the end effector.

In some of the above methods, the end effector may be positioned in arelatively coarse manner, the gas cushion may be removed from the firstjoint to lock in the relatively course position of the end effector, theend effector may then be positioned in a relatively fine manner, andthen the gas cushion may be removed from the second joint to lock in therelatively fine position of the end effector.

Some methods may include a step of removably attaching the base of thedevice to a bone of a patient. In some of the above methods, a miniatureendoscope is moved relative to the end effector and into a cochlea.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which.

FIG. 1A is a cross-sectional side view showing an exemplary positioningdevice constructed according to aspects of the Detailed Description andhaving an articulating joint in a locked or fixed state.

FIG. 1B is a cross-sectional side view showing the positioning device ofFIG. 1A with the articulating joint in a movable state.

FIG. 1C is a partially broken away plan view showing the proximalportion of the articulating joint shown in FIG. 1A.

FIG. 1D is a cross-sectional side view showing a variation of theproximal portion of the articulating joint shown in FIG. 1A.

FIG. 2A is a side perspective view showing another embodiment of anarticulating joint.

FIG. 2B is a bottom perspective view showing the concave portion of thearticulating joint of FIG. 2A.

FIG. 2C is a bottom view showing the concave portion of the articulatingjoint of FIG. 2A.

FIG. 2D is a partially broken away top view showing the concave portionof the articulating joint of FIG. 2A.

FIG. 2E is a top view showing a variation of the concave portion of thearticulating joint of FIG. 2A.

FIGS. 3A-3D are various perspective views showing alternativeembodiments of positioning systems having one or more pairs of lockablearticulating joints.

FIGS. 4A-4C are various perspective views showing an embodiment of apositioning system mounted on a templar bone and having joints in seriesand in parallel.

FIG. 5A is a cross-sectional side view showing an alternative embodimentof an articulating joint.

FIG. 5B is an exploded cross-sectional side view showing thearticulating joint of FIG. 5A.

FIG. 5C is an exploded perspective view showing the articulating jointof FIG. 5A.

DETAILED DESCRIPTION

Referring to FIG. 1A, an exemplary positioning device 100 constructedaccording to aspects of the present invention is schematically shown.Device 100 includes an end effector 102 movably connected to base 104 byarticulating links 106 and 108. In this embodiment, end effector 102includes a through-hole 110 for receiving an object to be positioned(not shown in FIG. 1A). Base 104 may rest on or be attached to astationary reference surface. In alternative embodiments, base 104 maybe coupled to a movable apparatus, such as for coarse positioning ofdevice 100.

In the embodiment shown in FIG. 1A, articulating link 106 is rigidlyconnected to end effector 102, and articulating link 108 is rigidlyconnected to base 104. Links 106 and 108 are movably coupled together byjoint 112. In this embodiment, joint 112 is a spherical joint comprisinga proximal portion 114 located on link 108 and a distal portion 116located on link 106. Proximal portion 114 comprises an annular magnet118 fixed within an axial bore of proximal portion 114, such as by apress fit, adhesive, or molded therein. Distal portion 116 of joint 112includes a spherical member 120. Spherical member 120 comprises aferrous and/or magnetic material such that it is attracted to magnet118. In this manner, proximal portion 114 and distal portion 116 ofjoint 112 are drawn towards each other by magnetic attraction. In thisembodiment, proximal portion 114 includes a concave surface 121 havingsubstantially the same radius of curvature as that of spherical member120, thereby creating intimate contact between substantially all ofsurface 121 and a portion of the outer surface of spherical member 120.The combination of magnetic force and large surface area contact in thisembodiment causes spherical member 120 to be in a locked positionrelative to proximal portion 114 when in this configuration. As aconsequence of this fixed or locked configuration of joint 112, endeffector 102 is generally immovable relative to base 104.

Referring now to FIG. 1B, proximal portion 114 of joint 112 furthercomprises an inlet port 122 connected to a compressed air supply (orother compressed gas or fluid supply) by valve 124. Inlet port 122 is influid communication with channel 126 through the axial bore of proximalportion 114. Channel 126 is located adjacent to spherical member 120.When valve 124 is opened, compressed air flows from the supply throughchannel 126 with enough pressure to overcome the magnetic attractionbetween the proximal and distal portions of joint 112, urging sphericalmember 120 apart from mating concave surface 121. A thin air cushion 128is thus formed between spherical member 120 and concave surface 121 ascompresses air flows between the two and exits in the direction of thearrows labeled A. The farther that spherical member 120 moves away fromconcave surface 121, the lower the resulting air pressure between thetwo surfaces, because the air is allowed to escape more easily.Therefore, the pressurized air will only move spherical member 120 apredetermined distance away from mating surface 121, held in balance bythe equal and opposite force of magnetic attraction between magnet 118and spherical member 120. The strength and location of magnet 118, thepressure of the compressed air (or other gas), the surface area betweenspherical member 120 and mating surface 121, surface roughnesses, andother parameters may be selected such that air cushion 128 may be keptto a minimal thickness yet allows spherical member 120 to move freelyrelative to mating surface 121. In some embodiments, air cushion 128 hasa thickness of about 5 microns or less.

With the above arrangement, valve 124 may be opened to allow joint 112to be changed from a fixed state to a movable state by creating an aircushion 128 between the proximal portion 114 and the distal portion 116.When joint 112 is in the movable state, as shown in FIG. 1B, endeffector 102 may freely be moved by hand or other means to any desiredposition. Air cushion 128 allows end effector 102 to be moved with verylittle friction. Valve 124 may then be closed to remove air cushion 128and cause proximal portion 114 and distal portion 116 to contact eachother, thus changing joint 112 from the movable state to the fixedstate, as shown in FIG. 1A. Because the thickness of air cushion 128 maybe very small in some embodiments, there is no appreciable movement whenjoint 112 is changed from the movable state to the fixed state.

In some embodiments, joint 112 may be configured such that it is freelymovable when valve 124 is sufficiently open, and movable with someresistance when valve 124 is opened to a lesser extend. In other words,when valve 124 is only partially open, the air cushion formed issufficient to partially overcome the magnetic attraction between theproximal and distal portions of joint 112, but is not so thick as toprovide complete separation between the entirety of the mating surfaces.This arrangement may be desirable when some fixation force is desired toovercome gravity or other small disturbing forces, but still allow theposition of end effector 102 to be adjusted before being locked.

In the embodiment shown in FIG. 1B, joint 112 (and therefore also endeffector 102) may be moved in three degrees of rotational freedom whenin the movable state. These degrees of freedom can be described as roll,pitch and yaw, as depicted by arrows labeled R, P and Y, respectively.In other embodiments (not shown), joint 112 may be constrained to justtwo or one degrees of freedom.

To increase the holding force between spherical member 120 and matingsurface 121 when joint 112 is in the fixed state, one or both of thesesurfaces may be roughened. This may be accomplished by choice ofcomponent material(s), coating the surface(s), and/or various finishingtechniques such as sand blasting. In some embodiments, high-frictioncoatings or base materials may be used to increase friction withoutadding surface roughness, thereby increasing the precision of the joint.Porous surface materials may also be used to increase performance inboth the locked and movable states of the joint.

Referring to FIG. 1C, a partially broken away axial view of proximalportion 114 is shown, illustrating magnet 118 within the body 130 ofproximal portion 114.

Referring to FIG. 1D, an alternate embodiment of proximal portion 114′is shown. As depicted, two (or more) annular magnets 118 may be axiallyaligned to provide greater holding strength. Also, the upper magnet neednot be embedded below concave surface 121 as in the embodiment shown inFIGS. 1A-1C, but may be fabricated to form part or all of surface 121itself. Along these lines, an alternate proximal portion (not shown) maybe formed from a unitary piece of ferrous and/or magnetic material, suchas by sintering, grinding, and/or other fabrication techniques known tothose skilled in the art.

Referring now to FIGS. 2A-2D, various views of another embodiment areshown. In this embodiment, small cylindrically-shaped magnets 202 arearranged in an off-axis manner. Three magnets 202 may be equally spacedaround the central axis of proximal portion 204 of spherical joint 206.As can best be seen in FIG. 2A, the individual axes of magnets 202 maybe generally aligned with the center of spherical member 208. Theproximal end 210 of an air channel can be seen in FIGS. 2A-2C, while thedistal end 212 of the air channel can be seen in the middle of concavemating surface 214 in FIG. 2D.

Referring to FIG. 2E, a variation of the embodiment of FIG. 2A-2D isshown. In this embodiment, magnets 202 protrude through concavespherical surface 214′ rather than being embedded below the surface.Magnets 202 may stand proud of surface 214′, be flush with it, or beslightly recessed. In some embodiments, the body of proximal portion204′ may be fabricated by placing magnets 202 on spherical member 208 ina desired spacing, placing spherical member 208 with attached magnets202 at least partially into a mold cavity, and filling the mold cavitywith a hardenable substance around magnets 202, such as with athermoplastic, thermosetting plastic, resin or epoxy. Once the substancehas hardened, spherical member 208 may then be separated from magnets202 and the hardenable substance (a mold release may need to be appliedto spherical member 208 before molding), leaving the concave matingsurface 214 and magnets as shown in FIG. 2E.

In some embodiments (not shown), the distal end 212 of the air channelmay be made larger, and/or a network of shallow grooves in fluidcommunication with the distal end 212 of the air channel may be providedalong concave surface 214. This arrangement provides a larger area ofthe pressurized air when it is first activated to move spherical member208 away from magnets 202. Accordingly, a lower pressure air supply maybe used for a given magnet arrangement, and oscillations of thespherical member 208 when first separated from magnets 202 may beavoided.

In some embodiments, fewer or more than the three magnets 202 shown inFIGS. 2A-2E are used. High energy magnets may be sued to allow for agreater magnetic attraction force in a smaller package.

In some embodiments, the positions of the ball and socket members arereversed. In other words, spherical member 120 or 208 may be located onthe proximal portion of the articulating link and mating concave surface121 or 214 may be located on the distal portion, opposite of thearrangement shown in FIGS. 1A and 1B. In some embodiments, the base maybe located beside or above the end effector, mounted at an angle, and/ormounted on a movable platform.

While only spherical articulating joints have been discussed up to thispoint, it is to be understood that other types of kinematic joints maybe used to form bearing and braking mechanisms. For example, using theconcepts described above, a revolute joint may be constructed (onedegree of freedom), or a prismatic joint (one degree of freedom), acylindrical joint (two degrees of freedom), a planar joint (two or threedegrees of freedom), or a spherical joint (with up to three degrees offreedom). Combinations of these joints may also be used in series and/orparallel, as will be described in more detail below. In general, eachjoint may be formed by a pair of surfaces that have congruent areas ofcontact.

Referring to FIG. 3A, a positioning apparatus 300 is shown having twoarticulating joints 302 and 304 in series. Joint 304 is similar to thosepreviously described, having a spherical member 306 forming its distalportion, and a mating concave member 308 with magnets 310 forming itsproximal portion. Joint 302 has a similar construction, with a largerspherical member 312 forming its proximal portion, and a mating concavemember 314 with magnets 310 forming its distal portion. A single airsupply 316 may be used to simultaneously activate both joints 302 and304. When compressed air is introduced through common air supply 316, athin air cushion is formed between spherical member 306 and matingconcave member 308, and also between spherical member 312 and matingconcave member 314. Each of the two air cushions allows one of thearticulating joints 302 and 304 to move in up to three degrees offreedom, thereby allowing the mechanism to move in up to six degrees offreedom.

In the embodiment shown in FIG. 3A, articulating joints 302 and 304 areseparated by a rigid link 320. An internal air channel (not shown)running longitudinally within link 320 delivers compressed air fromcommon air supply 316 to each of the two joints 302, 304. In someembodiments, this internal air channel is formed by a bore of constantdiameter extending between an office in the concave member 308 of joint302 and an orifice in the concave member 314 of joint 304, and havingthe same diameter as the two orifices. In other embodiments, it may bedesirable to maximize the diameter of the internal air channel, or tootherwise provide a plenum between joints 302 and 304. Such arrangementscan avoid oscillations that may otherwise occur in joints 302 and 304.In some embodiments, the internal channel has a minimum lateralcross-sectional area that is at least four times as large as a lateralcross-sectional area of each of the orifices. In some embodiments, theinternal channel has a maximum lateral cross-sectional area that is atleast one-half as large as a minimum total lateral cross-sectional areaof link 320.

Referring to FIG. 3B, a positioning apparatus 300′ similar topositioning apparatus 300 shown in FIG. 3A. Apparatus 300′ includes aninstrument 322 that may be slidably received in a lumen within endeffector 318. Instrument 322 may be medical device, such as miniatureendoscope having a first portion configured to be precisely receivedwithin the end effector lumen and a second portion configured forentering a human cochlea.

In operation, compressed air may be supplied to common supply 316 aspreviously described, allowing joints 302 and 304 to freely articulate.It should be noted that the arrangement of positioning apparatus 300′allows instrument 322 to remain in a particular orientation if desiredas it is moved laterally and/or longitudinally in three dimensions. Onceinstrument 322 has been positioned and oriented as desired, the airsupply to joints 302 and 304 may be interrupted. This allows magnets 310to lock joints 302 and 304, thereby holding instrument 322 precisely inplace. In other embodiments, the air supply to joints 302 and 304 may beindependently controlled, allowing only one joint to be locked while theother joint is still free to move.

Referring to FIG. 3C, another embodiment of a positioning system isshown. Positioning system 324 includes four articulating joints 326,328, 330 and 332 connected in series between base 334 and end effector318. In this embodiment, each joint is a spherical joint that ischangeable between a movable state and a fixed or locked state, similarto those previously described. Joints 326 and 328 share a first commoncompressed air supply line 336 within link 338. Joints 330 and 332 sharea second common compressed air supply line 340 within link 342. Joints328 and 330 are spaced apart by link 344.

First supply line 336 and second supply line 340 may be connected to asingle control valve (not shown) such that all four joints 326, 328, 330and 332 are either in a movable state or a locked state at the sametime. Alternatively, the first and second supply lines 336 and 340 maybe independently controlled. In this manner, the coarse positioning ofinstrument 322 may be obtained with all four joints, or at least joints326 and 328 being in the movable state. Joints 326 and 328 may then belocked in position by turning off the air supply to first common supplyline 336. Joints 330 and 332 may be left in the movable state so thatfine positioning of instrument 322 may be performed. The air supply tosecond common supply line 340 may then be turned off to fully lock theposition of instrument 322. To control one or both of the air supplylines 336 and 340, manually or electrically actuated valve(s) may beused. To further control the valves, foot pedals, electronic switches,and/or electronic or mechanical controllers may be used. The footpedal(s) and/or electronic switches may control the air supply in abinary fashion such that it is either fully on or fully off, or mayallow variable control so that the air supply may be gradually turned onor off In other embodiments, two, three, four or more articulationjoints may be independently controlled.

Referring to FIG. 3D, another embodiment of a positioning system isshown. Positioning system 350 includes four articulating joints 352,354, 356, and 358 connected in series between base 360 and end effector362. In this embodiment, the proximal portion of joint 352 includes alarge spherical member 364 rigidly attached to base 360. In otherembodiments, spherical member 364 may form a movable and lockable jointwith base 360.

Referring to FIGS. 4A-4C, another embodiment of a positioning system isshown. FIG. 4A shows the base 400 of system 402. Base 400 includes alarge spherical member 404, similar to base 360 shown in FIG. 3D. Base400 is shown attached to a temporal bone 406 adjacent to the externalacoustic meatus 408 of the ear canal. Attachment may be made using oneor more bone screws (not shown) passing through or formed in base 400and temporarily extending into the temporal bone 406. Such a mounting onbone provides a secure base from which to precisely position aninstrument with system 402, such as a miniature endoscope for insertioninto the cochlea as previously described.

FIGS. 4B and 4C show the articulating joints of positioning system 402.In this exemplary embodiment, system 402 includes a first series 410 ofarticulating joints and a second series 412 of articulating joints. Thefirst series 410 includes joints 414, 416 and 418. The second seriesincludes joints 420, 422 and 424. Spherical member 404 serves as acommon proximal portion for both joints 414 and 420. When in the movablestate, the distal, concave portion of each of joints 414 and 420 maymove across spherical member 404. End effector 426 includes a sectionthat serves as a common distal portion for both joints 418 and 424. Inthis arrangement, the first and second series 410 and 412 of joints arearranged in parallel to connect end effector 426 with base 400. With twoseries of joints arranged in parallel as shown in this example, endeffector 426 may be held more stably while still being able to bepositioned in a wide range of positions and orientations.

End effector 426 also includes a section for receiving an instrument428, such as a miniature endoscope, and a handle section 430 formanually manipulating the position and orientation of instrument 428when the articulating joints are in their movable state.

Using the joint construction of the previously described exemplaryembodiments, there is little movement of the joints when they arechanged from there moveable state to their fixed state. In manyembodiments, this movement is less than 5 microns (the thickness of theair cushion between the parts of the joint.) This very small movementmay become even more important when six or more joints are used incombination as shown. This inventive arrangement allows an instrument tobe precisely positioned, and then locked firmly in place withoutsignificant movement occurring during the locking of the joints.

In other embodiments, any number or type of articulating joints may bearranged in series, parallel or both to form lockable, precisionpositioning systems similar to those described above.

In some embodiments (not shown), one or more joints may be formed withpairs of magnets aligned in such a way that the magnetic attractionbetween the opposing magnets provides a self centering effect. Forexample, instead of using a ferrous sphere as one portion of a lockablejoint, a sphere having magnet(s) or ferrous portion(s) aligned withmagnet(s) on the concave portion of the joint can be used, causing thejoint to seek a particular orientation of the sphere relative to theconcave portion. This type of arrangement can be used to at leastpartially overcome the effects of gravity or other disturbing forceswhen the joint is in the moveable state.

In some embodiments, an electromagnet can be provided in thearticulating joint(s). The electromagnet may be energized to lock thejoint without interrupting the air flow, or may be used to increase thefrictional engagement of the joint when locked.

In some embodiments, vacuum between the two portions of a joint may beused to further lock the joint from movement.

In some embodiments, the joint can be configured to act as a mechanicalfuse for overload protection. By properly selecting the characteristicsof both sides of a joint, the joint can be designed to come apart when apredetermined load is reached. This can protect other parts of thepositioning system from being damaged by excessive loading.

Referring to FIGS. 5A-5C, an alternative embodiment articulating joint500 is shown. In this exemplary embodiment, joint 500 includes a plastichousing 502, a ferromagnetic liner 504, a permanent magnet 506, and asteel ball 508. As best seen in FIG. 5A, liner 504 is cup shaped and isreceived within housing 502. Magnet 506 is received within liner 504 andresides between the bottom of liner 504 and steel ball 508 when joint500 is assembled. An axial lumen 510 is provided in housing 502 thatextends through liner 504 and magnet 506 to allow compressed air to besupplied between ball 508 and a mating concave surface 512 formed inhousing 502.

With the above arrangement, an effective connection can be made betweenboth poles of magnet 506 (the top and bottom surfaces in thisembodiment) and steel ball 508. This completes the magnetic circuitbetween magnet 506 and steel ball 508 and significantly reduces the airgap between the two, thereby reducing the reluctance of the magneticcircuit. Such an arrangement can serve to increase the attractive forcebetween magnet 506 and ball 508. It can also minimize the magneticinfluence between neighboring joints, thereby reducing undesirableattractive and/or repulsive forces from one joint on another.

In other embodiments, a ferromagnetic body can be used in a similarmanner to optimize magnetic flux. For example, in embodiments havingplanar joints (not shown), a ferromagnetic body with a particularconfiguration can be added to the joint to allow a magnetic circuit tobe completed between both poles of a magnet in one side of the joint anda ferrous material located in the other side of the joint.

In some embodiments, multiple instruments may be located at the distalend and/or at intermediate positions along the length of thearticulating positioning system. For example, a surgical instrument maybe located at the distal end, a suction device may be located at linkproximal to the surgical instrument, and a lighting apparatus may belocated at a link proximal to the suction device. In use, the moreproximal link holding the lighting apparatus may be positioned andlocked first, then the suction device link may be positioned and locked,and then the surgical instrument may be positioned and locked.

While exemplary embodiments constructed according to aspects of thepresent invention have been shown and described herein, it will beobvious to those skilled in the art that such embodiments are providedby way of example only. Numerous variations, changes, and substitutionswill now occur to those skilled in the art without departing from theinvention. For example, other means of inducing attractive forcesbetween bodies may be used including electro-magnets, springs,capacitive and electrostatic forces, as well as other nuclear andinertial effects that give rise to force. Surface materials, textures,porosities and geometries may be selected to increase friction in thelocked state. As an example of surface geometries that may be used,mating splines may be located on opposing portions of a joint to lockthe joint in one of a series of discrete positions when the joint ischanged to a fixed state. It should be understood that variousalternatives to the embodiments of the invention described herein may beemployed in practicing the invention.

What is claimed is:
 1. A positioning system comprising: a plurality oflockable spheres, each of the plurality of lockable spheres comprising abase portion and a spherical member coupled together by magneticattraction and configured to be intermittently separated by apressurized gas cushion, each of the plurality of lockable spheresconfigured to be changeable between a movable state in which the baseportion and spherical member are separated by the pressurized gascushion and rotatable relative to each other in three degrees ofrotational freedom, and a fixed state in which the base portion andspherical member contact each other and relative movement is therebyimpeded.
 2. The system of claim 1, wherein each of the plurality oflockable spheres shares a common base portion.
 3. The system of claim 2,wherein at least two of the plurality of lockable spheres have aninterruptible pressurized gas cushion that is separate from the other ofthe two.
 4. The system of claim 1, wherein at least one of the sphericalmembers and or base portions has a surface that has been roughened toincrease a holding force between the spherical member and a matingsurface of the base portion when the associated lockable sphere is inthe fixed state.
 5. The system of claim 4, wherein the surface of the atleast one spherical member and or base portion has been roughened bycoating the surface.
 6. The system of claim 4, wherein the surface ofthe at least one spherical member and or base portion has been roughenedby sand blasting.
 7. The system of claim 4, wherein the surface of theat least one spherical member and or base portion has been roughened bythe use of a porous surface material.
 8. The system of claim 1, whereinat least one of the plurality of lockable spheres comprises anelectromagnet that can be energized to lock the lockable sphere.
 9. Thesystem of claim 8, wherein the electromagnet can be energized to lockthe lockable sphere without interrupting an air flow that creates thepressurized gas cushion in the lockable sphere.
 10. The system of claim8, wherein the electromagnet can be energized in conjunction withinterrupting an air flow that creates the pressurized gas cushion in thelockable sphere to lock the lockable sphere.
 11. The system of claim 1,wherein at least one of the plurality of lockable spheres comprises apermanent magnet configured to lock the lockable sphere in the fixedstate once the pressurized gas cushion is removed.
 12. The system ofclaim 11, wherein the permanent magnet is located in the base portion ofthe at least one lockable sphere.
 13. The system of claim 12, whereinthe base portion further comprises a ferromagnetic liner locatedcoaxially with the permanent magnet.
 14. A method of positioning anobject, the method comprising: providing a positioning system having aplurality of lockable spheres, each of the plurality of lockable spherescomprising a base portion and a spherical member coupled together bymagnetic attraction and configured to be intermittently separated by apressurized gas cushion, each of the plurality of lockable spheresconfigured to be changeable between a movable state in which the baseportion and spherical member are separated by the pressurized gascushion and rotatable relative to each other in three degrees ofrotational freedom, and a fixed state in which the base portion andspherical member contact each other and relative movement is therebyimpeded; providing a pressurized gas supply to create a pressurized gascushion in at least one of the plurality of lockable spheres, therebyputting the at least one lockable sphere in the movable state andallowing movement of the object; and removing the pressurized gas supplyfrom the at least one lockable sphere, thereby putting the at least onelockable sphere in the fixed state and inhibiting movement of theobject.
 15. The method of claim 14, comprising putting at least one ofthe lockable spheres in the fixed state and putting at least another oneof the lockable spheres in the movable state to inhibit full movement ofthe object while allowing partial movement of the object.
 16. The methodof claim 14, comprising putting each of the plurality of the lockablespheres in the fixed state to fully constrain the object from movement.17. The method of claim 14, wherein at least one of the sphericalmembers and or base portions has a surface that has been roughened toincrease a holding force between the spherical member and a matingsurface of the base portion when the associated lockable sphere is inthe fixed state.
 18. The method of claim 14, wherein the base portion ofat least one of the lockable spheres comprises a permanent magnet and aferromagnetic liner located coaxially with the permanent magnet.